Organic vapor jet print head for depositing thin film features with high thickness uniformity

ABSTRACT

Devices for deposition of material via organic vapor jet printing (OVJP) and similar techniques are provided. The depositor includes delivery channels ending in delivery apertures, where the delivery channels are flared as they approach the delivery apertures, and/or have a trapezoidal shape. The depositors are suitable for fabricating OLEDs and OLED components and similar devices.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a non-provisional of, and claims the prioritybenefit of U.S. Patent Application Ser. No. 62/616,571, filed Jan. 12,2018, the entire contents of which are incorporated herein by reference.

FIELD

The present invention relates to devices and techniques for depositingmaterial for use in devices such as organic light emitting diodes, anddevices including the same.

BACKGROUND

Opto-electronic devices that make use of organic materials are becomingincreasingly desirable for a number of reasons. Many of the materialsused to make such devices are relatively inexpensive, so organicopto-electronic devices have the potential for cost advantages overinorganic devices. In addition, the inherent properties of organicmaterials, such as their flexibility, may make them well suited forparticular applications such as fabrication on a flexible substrate.Examples of organic opto-electronic devices include organic lightemitting diodes/devices (OLEDs), organic phototransistors, organicphotovoltaic cells, and organic photodetectors. For OLEDs, the organicmaterials may have performance advantages over conventional materials.For example, the wavelength at which an organic emissive layer emitslight may generally be readily tuned with appropriate dopants.

OLEDs make use of thin organic films that emit light when voltage isapplied across the device. OLEDs are becoming an increasinglyinteresting technology for use in applications such as flat paneldisplays, illumination, and backlighting. Several OLED materials andconfigurations are described in U.S. Pat. Nos. 5,844,363, 6,303,238, and5,707,745, which are incorporated herein by reference in their entirety.

One application for phosphorescent emissive molecules is a full colordisplay. Industry standards for such a display call for pixels adaptedto emit particular colors, referred to as “saturated” colors. Inparticular, these standards call for saturated red, green, and bluepixels. Alternatively the OLED can be designed to emit white light. Inconventional liquid crystal displays emission from a white backlight isfiltered using absorption filters to produce red, green and blueemission. The same technique can also be used with OLEDs. The white OLEDcan be either a single EML device or a stack structure. Color may bemeasured using CIE coordinates, which are well known to the art.

As used herein, the term “organic” includes polymeric materials as wellas small molecule organic materials that may be used to fabricateorganic opto-electronic devices. “Small molecule” refers to any organicmaterial that is not a polymer, and “small molecules” may actually bequite large Small molecules may include repeat units in somecircumstances. For example, using a long chain alkyl group as asubstituent does not remove a molecule from the “small molecule” class.Small molecules may also be incorporated into polymers, for example as apendent group on a polymer backbone or as a part of the backbone Smallmolecules may also serve as the core moiety of a dendrimer, whichconsists of a series of chemical shells built on the core moiety. Thecore moiety of a dendrimer may be a fluorescent or phosphorescent smallmolecule emitter. A dendrimer may be a “small molecule,” and it isbelieved that all dendrimers currently used in the field of OLEDs aresmall molecules.

As used herein, “top” means furthest away from the substrate, while“bottom” means closest to the substrate. Where a first layer isdescribed as “disposed over” a second layer, the first layer is disposedfurther away from substrate. There may be other layers between the firstand second layer, unless it is specified that the first layer is “incontact with” the second layer. For example, a cathode may be describedas “disposed over” an anode, even though there are various organiclayers in between.

As used herein, “solution processible” means capable of being dissolved,dispersed, or transported in and/or deposited from a liquid medium,either in solution or suspension form.

A ligand may be referred to as “photoactive” when it is believed thatthe ligand directly contributes to the photoactive properties of anemissive material. A ligand may be referred to as “ancillary” when it isbelieved that the ligand does not contribute to the photoactiveproperties of an emissive material, although an ancillary ligand mayalter the properties of a photoactive ligand.

As used herein, and as would be generally understood by one skilled inthe art, a first “Highest Occupied Molecular Orbital” (HOMO) or “LowestUnoccupied Molecular Orbital” (LUMO) energy level is “greater than” or“higher than” a second HOMO or LUMO energy level if the first energylevel is closer to the vacuum energy level. Since ionization potentials(IP) are measured as a negative energy relative to a vacuum level, ahigher HOMO energy level corresponds to an IP having a smaller absolutevalue (an IP that is less negative). Similarly, a higher LUMO energylevel corresponds to an electron affinity (EA) having a smaller absolutevalue (an EA that is less negative). On a conventional energy leveldiagram, with the vacuum level at the top, the LUMO energy level of amaterial is higher than the HOMO energy level of the same material. A“higher” HOMO or LUMO energy level appears closer to the top of such adiagram than a “lower” HOMO or LUMO energy level.

As used herein, and as would be generally understood by one skilled inthe art, a first work function is “greater than” or “higher than” asecond work function if the first work function has a higher absolutevalue. Because work functions are generally measured as negative numbersrelative to vacuum level, this means that a “higher” work function ismore negative. On a conventional energy level diagram, with the vacuumlevel at the top, a “higher” work function is illustrated as furtheraway from the vacuum level in the downward direction. Thus, thedefinitions of HOMO and LUMO energy levels follow a different conventionthan work functions.

More details on OLEDs, and the definitions described above, can be foundin U.S. Pat. No. 7,279,704, which is incorporated herein by reference inits entirety.

SUMMARY

According to an embodiment, a device for deposition of a material onto asubstrate is provided, which includes a nozzle block having a firstexhaust aperture; a second exhaust aperture; and a first deliverychannel having a first end that forms a first delivery aperture disposedbetween the first exhaust aperture and the second exhaust aperture andcloser to the first exhaust aperture than the second exhaust aperture,where the first delivery channel is wider at a first portion than at asecond portion, the first portion being closer to the delivery aperturethat the second portion, and the first portion is in direct fluidcommunication with the first delivery aperture and the second portion isin direct fluid communication with the first portion. That is, thedelivery channel has a flare at the delivery aperture. The nozzle blockmay include a second delivery channel having a first end that forms asecond delivery aperture disposed between the first exhaust aperture andthe second exhaust aperture, where the second delivery aperture isoffset from the first delivery aperture along an axis of the nozzle. Theside wall of the delivery channel at the flare may form an angle in therange of 30-60° with the surface of the nozzle block. The first andsecond exhaust apertures may be rectangular, with the longest edge ofeach being arranged along a direction of relative movement of the deviceand the substrate when the device is in operation. The delivery aperturemay have a flare width of 6-12 μm. The delivery aperture(s) may berectangular, trapezoidal, or any other suitable shape. For a trapezoidaldelivery aperture, an angle α between a long center axis of the deliveryaperture and a longest edge of the delivery aperture may be in the rangeof 1.1°-1.7°. The nozzle block may further include third and fourthexhaust apertures and a second delivery channel having a first end thatforms a first delivery aperture disposed between the third exhaustaperture and the fourth exhaust aperture and closer to the fourthexhaust aperture than the third exhaust aperture, with the seconddelivery channel being flared at the corresponding delivery aperture.The second delivery channel, third exhaust aperture, and fourth exhaustaperture may be disposed in a trailing position in the nozzle blockrelative to the first delivery channel, first exhaust aperture, andsecond exhaust aperture. The group of the first and second exhaustapertures may be offset from the group of the third and fourth deliveryapertures along a direction perpendicular to the leading/trailing axis.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an organic light emitting device.

FIG. 2 shows an inverted organic light emitting device that does nothave a separate electron transport layer.

FIGS. 3A and 3B show an OVJP depositor with a diverging deliveryaperture as seen from the substrate and a cross sectional view of theinternal channels of the depositor according to an embodiment disclosedherein.

FIG. 4 shows an expanded cross sectional view of an OVJP depositor witha diverging delivery aperture as shown in FIGS. 3A-3B with exampledimensions according to an embodiment disclosed herein.

FIG. 5 shows a three dimensional rendering of an OVJP depositor with adiverging delivery aperture according to an embodiment disclosed herein.

FIG. 6 shows deposition profiles generated by OVJP depositors withvarious degrees of delivery aperture divergence according to embodimentsdisclosed herein.

FIGS. 7A and 7B show contour plots of feature thickness uniformitygenerated by depositors with diverging delivery apertures for variousdepositor geometries according to embodiments disclosed herein.

FIGS. 8A and 8B show plots of printed feature size and depositorefficiency as a function of fly height for depositors with varyingdegrees of delivery aperture divergence according to embodimentsdisclosed herein.

FIG. 9 shows an example of the change in figure of merit obtainable by adepositor with a diverging aperture configured to operate at a given flyheight, as a function of fly height according to an embodiment disclosedherein.

FIG. 10 shows a deposition profile generated by the upper half ofdepositors with varying degrees of delivery aperture divergenceaccording to embodiments disclosed herein.

FIGS. 11A and 11B illustrate examples of the dependence of theuniformity of a composite feature on the shape of the component featuresused to construct the feature according to embodiments disclosed herein.

FIG. 12A shows an OVJP depositor with trapezoidal delivery apertures asseen from the substrate according to an embodiment disclosed herein.

FIG. 12B shows a three-dimensional view of an OVJP depositor fabricatedwith deep reactive ion etching that manifests an undercut according toan embodiment disclosed herein.

FIG. 13 shows a photograph of an organic thin film feature deposited bya stationary OVJP depositor with trapezoidal delivery aperturesaccording to an embodiment disclosed herein, with gradations inthickness indicated by interference fringes.

FIG. 14 shows a plot of the normalized gas flow per unit length throughtrapezoidal delivery and apertures and bowtie shaped exhaust aperturesaccording to embodiments disclosed herein.

FIG. 15A shows examples of deposition profiles generated by OVJPdepositors with various degrees of aperture taper according toembodiments disclosed herein.

FIG. 15B shows a comparison of deposition profiles for a depositor witha trapezoidal delivery aperture and a depositor with a rectangulardelivery aperture according to embodiments disclosed herein.

FIG. 16 shows a plot of film thickness uniformity achieved by differentdepositors with trapezoidal apertures as a function of fly heightaccording to embodiments disclosed herein.

FIG. 17A shows a plot of material deposition rates achieved bydepositors with trapezoidal apertures according to embodiments disclosedherein, as a function of fly height.

FIG. 17B shows a plot of feature size printed by different depositorswith trapezoidal apertures according to embodiments disclosed herein asa function of fly height.

FIG. 18 shows a plot of the figure of merit (FOM) for differentdepositors with trapezoidal apertures according to embodiments disclosedherein as a function of fly height.

FIGS. 19A and 19B show contour plots of the deposition field onto asubstrate generated by depositors with trapezoidal and rectangulardelivery apertures according to embodiments disclosed herein.

FIG. 20 shows a deposition profile generated by an upper half of adepositor with aperture sides defined by varying degrees of undercutaccording to embodiments disclosed herein.

FIG. 21 shows the aperture configuration of a depositor divided intomirror image sections arranged in two offset ranks according to anembodiment disclosed herein.

FIG. 22 show a three dimensional rendering of an array of two-rankdepositors according to an embodiment disclosed herein.

FIG. 23 shows deposition profiles produced by a single rank of atwo-rank depositor according to an embodiment disclosed herein.

FIG. 24 shows deposition profiles produces by a two-rank depositor withvarious offsets between its ranks according to an embodiment disclosedherein.

FIG. 25 shows an example arrangement of a pixel with red, green, andblue subpixels that may be suitable for a display printing applicationaccording to an embodiment disclosed herein.

FIG. 26A shows dimensions of a blue subpixel overlaid with a depositionprofile of a two-rank depositor designed to print the blue subpixelaccording to an embodiment disclosed herein.

FIG. 26B shows the dimensions of a red or green subpixel overlaid withthe deposition profile of a two-rank depositor configured to print thered or green subpixel according to an embodiment disclosed herein.

FIG. 27A shows an assembly of three wafers to make a two-rank depositoraccording to an embodiment disclosed herein, viewed from the plane ofthe depositor apertures.

FIG. 27B shows routing of delivery and exhaust channels through across-section of a die containing two-rank depositors according to anembodiment disclosed herein.

FIG. 28A shows channel traces of the first rank of a depositor accordingto an embodiment disclosed herein.

FIG. 28B shows channel traces of the second rank of a depositoraccording to an embodiment disclosed herein.

DETAILED DESCRIPTION

Generally, an OLED comprises at least one organic layer disposed betweenand electrically connected to an anode and a cathode. When a current isapplied, the anode injects holes and the cathode injects electrons intothe organic layer(s). The injected holes and electrons each migratetoward the oppositely charged electrode. When an electron and holelocalize on the same molecule, an “exciton,” which is a localizedelectron-hole pair having an excited energy state, is formed. Light isemitted when the exciton relaxes via a photoemissive mechanism. In somecases, the exciton may be localized on an excimer or an exciplex.Non-radiative mechanisms, such as thermal relaxation, may also occur,but are generally considered undesirable.

The initial OLEDs used emissive molecules that emitted light from theirsinglet states (“fluorescence”) as disclosed, for example, in U.S. Pat.No. 4,769,292, which is incorporated by reference in its entirety.Fluorescent emission generally occurs in a time frame of less than 10nanoseconds.

More recently, OLEDs having emissive materials that emit light fromtriplet states (“phosphorescence”) have been demonstrated. Baldo et al.,“Highly Efficient Phosphorescent Emission from OrganicElectroluminescent Devices,” Nature, vol. 395, 151-154, 1998;(“Baldo-I”) and Baldo et al., “Very high-efficiency green organiclight-emitting devices based on electrophosphorescence,” Appl. Phys.Lett., vol. 75, No. 3, 4-6 (1999) (“Baldo-II”), are incorporated byreference in their entireties. Phosphorescence is described in moredetail in U.S. Pat. No. 7,279,704 at cols. 5-6, which are incorporatedby reference.

FIG. 1 shows an organic light emitting device 100. The figures are notnecessarily drawn to scale. Device 100 may include a substrate 110, ananode 115, a hole injection layer 120, a hole transport layer 125, anelectron blocking layer 130, an emissive layer 135, a hole blockinglayer 140, an electron transport layer 145, an electron injection layer150, a protective layer 155, a cathode 160, and a barrier layer 170.Cathode 160 is a compound cathode having a first conductive layer 162and a second conductive layer 164. Device 100 may be fabricated bydepositing the layers described, in order. The properties and functionsof these various layers, as well as example materials, are described inmore detail in U.S. Pat. No. 7,279,704 at cols. 6-10, which areincorporated by reference.

More examples for each of these layers are available. For example, aflexible and transparent substrate-anode combination is disclosed inU.S. Pat. No. 5,844,363, which is incorporated by reference in itsentirety. An example of a p-doped hole transport layer is m-MTDATA dopedwith F₄-TCNQ at a molar ratio of 50:1, as disclosed in U.S. PatentApplication Publication No. 2003/0230980, which is incorporated byreference in its entirety. Examples of emissive and host materials aredisclosed in U.S. Pat. No. 6,303,238 to Thompson et al., which isincorporated by reference in its entirety. An example of an n-dopedelectron transport layer is BPhen doped with Li at a molar ratio of 1:1,as disclosed in U.S. Patent Application Publication No. 2003/0230980,which is incorporated by reference in its entirety. U.S. Pat. Nos.5,703,436 and 5,707,745, which are incorporated by reference in theirentireties, disclose examples of cathodes including compound cathodeshaving a thin layer of metal such as Mg:Ag with an overlyingtransparent, electrically-conductive, sputter-deposited ITO layer. Thetheory and use of blocking layers is described in more detail in U.S.Pat. No. 6,097,147 and U.S. Patent Application Publication No.2003/0230980, which are incorporated by reference in their entireties.Examples of injection layers are provided in U.S. Patent ApplicationPublication No. 2004/0174116, which is incorporated by reference in itsentirety. A description of protective layers may be found in U.S. PatentApplication Publication No. 2004/0174116, which is incorporated byreference in its entirety.

FIG. 2 shows an inverted OLED 200. The device includes a substrate 210,a cathode 215, an emissive layer 220, a hole transport layer 225, and ananode 230. Device 200 may be fabricated by depositing the layersdescribed, in order. Because the most common OLED configuration has acathode disposed over the anode, and device 200 has cathode 215 disposedunder anode 230, device 200 may be referred to as an “inverted” OLED.Materials similar to those described with respect to device 100 may beused in the corresponding layers of device 200. FIG. 2 provides oneexample of how some layers may be omitted from the structure of device100.

The simple layered structure illustrated in FIGS. 1 and 2 is provided byway of non-limiting example, and it is understood that embodiments ofthe invention may be used in connection with a wide variety of otherstructures. The specific materials and structures described areexemplary in nature, and other materials and structures may be used.Functional OLEDs may be achieved by combining the various layersdescribed in different ways, or layers may be omitted entirely, based ondesign, performance, and cost factors. Other layers not specificallydescribed may also be included. Materials other than those specificallydescribed may be used. Although many of the examples provided hereindescribe various layers as comprising a single material, it isunderstood that combinations of materials, such as a mixture of host anddopant, or more generally a mixture, may be used. Also, the layers mayhave various sublayers. The names given to the various layers herein arenot intended to be strictly limiting. For example, in device 200, holetransport layer 225 transports holes and injects holes into emissivelayer 220, and may be described as a hole transport layer or a holeinjection layer. In one embodiment, an OLED may be described as havingan “organic layer” disposed between a cathode and an anode. This organiclayer may comprise a single layer, or may further comprise multiplelayers of different organic materials as described, for example, withrespect to FIGS. 1 and 2.

Structures and materials not specifically described may also be used,such as OLEDs comprised of polymeric materials (PLEDs) such as disclosedin U.S. Pat. No. 5,247,190 to Friend et al., which is incorporated byreference in its entirety. By way of further example, OLEDs having asingle organic layer may be used. OLEDs may be stacked, for example asdescribed in U.S. Pat. No. 5,707,745 to Forrest et al, which isincorporated by reference in its entirety. The OLED structure maydeviate from the simple layered structure illustrated in FIGS. 1 and 2.For example, the substrate may include an angled reflective surface toimprove out-coupling, such as a mesa structure as described in U.S. Pat.No. 6,091,195 to Forrest et al., and/or a pit structure as described inU.S. Pat. No. 5,834,893 to Bulovic et al., which are incorporated byreference in their entireties.

The various layers of OLEDs and similar devices disclosed herein may bedeposited by any suitable method. For the organic layers, preferredmethods include thermal evaporation, ink-jet, such as described in U.S.Pat. Nos. 6,013,982 and 6,087,196, which are incorporated by referencein their entireties, organic vapor phase deposition (OVPD), such asdescribed in U.S. Pat. No. 6,337,102 to Forrest et al., which isincorporated by reference in its entirety, and deposition by organicvapor jet printing (OVJP), such as described in U.S. Pat. No. 7,431,968,which is incorporated by reference in its entirety. Other suitabledeposition methods include spin coating and other solution basedprocesses. Solution based processes are preferably carried out innitrogen or an inert atmosphere. For the other layers, preferred methodsinclude thermal evaporation. Preferred patterning methods includedeposition through a mask, cold welding such as described in U.S. Pat.Nos. 6,294,398 and 6,468,819, which are incorporated by reference intheir entireties, and patterning associated with some of the depositionmethods such as ink jet and OVJD. Other methods may also be used. Thematerials to be deposited may be modified to make them compatible with aparticular deposition method. For example, substituents such as alkyland aryl groups, branched or unbranched, and preferably containing atleast 3 carbons, may be used in small molecules to enhance their abilityto undergo solution processing. Substituents having 20 carbons or moremay be used, and 3-20 carbons is a preferred range. Materials withasymmetric structures may have better solution processibility than thosehaving symmetric structures, because asymmetric materials may have alower tendency to recrystallize. Dendrimer substituents may be used toenhance the ability of small molecules to undergo solution processing.

Some OLEDs and similar devices may further optionally comprise a barrierlayer. One purpose of the barrier layer is to protect the electrodes andorganic layers from damaging exposure to harmful species in theenvironment including moisture, vapor and/or gases, etc. The barrierlayer may be deposited over, under or next to a substrate, an electrode,or over any other parts of a device including an edge. The barrier layermay comprise a single layer, or multiple layers. The barrier layer maybe formed by various known chemical vapor deposition techniques and mayinclude compositions having a single phase as well as compositionshaving multiple phases. Any suitable material or combination ofmaterials may be used for the barrier layer. The barrier layer mayincorporate an inorganic or an organic compound or both. The preferredbarrier layer comprises a mixture of a polymeric material and anon-polymeric material as described in U.S. Pat. No. 7,968,146, PCT Pat.Application Nos. PCT/US2007/023098 and PCT/US2009/042829, which areherein incorporated by reference in their entireties. To be considered a“mixture”, the aforesaid polymeric and non-polymeric materialscomprising the barrier layer should be deposited under the same reactionconditions and/or at the same time. The weight ratio of polymeric tonon-polymeric material may be in the range of 95:5 to 5:95. Thepolymeric material and the non-polymeric material may be created fromthe same precursor material. In one example, the mixture of a polymericmaterial and a non-polymeric material consists essentially of polymericsilicon and inorganic silicon.

Devices fabricated in accordance with embodiments of the invention canbe incorporated into a wide variety of electronic component modules (orunits) that can be incorporated into a variety of electronic products orintermediate components. Examples of such electronic products orintermediate components include display screens, lighting devices suchas discrete light source devices or lighting panels, etc. that can beutilized by the end-user product manufacturers. Such electroniccomponent modules can optionally include the driving electronics and/orpower source(s). Devices fabricated in accordance with embodiments ofthe invention can be incorporated into a wide variety of consumerproducts that have one or more of the electronic component modules (orunits) incorporated therein. A consumer product comprising an OLED thatincludes the compound of the present disclosure in the organic layer inthe OLED is disclosed. Such consumer products would include any kind ofproducts that include one or more light source(s) and/or one or more ofsome type of visual displays. Some examples of such consumer productsinclude flat panel displays, computer monitors, medical monitors,televisions, billboards, lights for interior or exterior illuminationand/or signaling, heads-up displays, fully or partially transparentdisplays, flexible displays, laser printers, telephones, mobile phones,tablets, phablets, personal digital assistants (PDAs), wearable devices,laptop computers, digital cameras, camcorders, viewfinders,micro-displays (displays that are less than 2 inches diagonal), 3-Ddisplays, virtual reality or augmented reality displays, vehicles, videowalls comprising multiple displays tiled together, theater or stadiumscreen, and a sign. Various control mechanisms may be used to controldevices fabricated in accordance with the present invention, includingpassive matrix and active matrix. Many of the devices are intended foruse in a temperature range comfortable to humans, such as 18 C to 30 C,and more preferably at room temperature (20-25 C), but could be usedoutside this temperature range, for example, from −40 C to 80 C.

The materials, structures, and techniques described herein may haveapplications in devices other than the fabrication of OLEDs. Forexample, other optoelectronic devices such as organic solar cells andorganic photodetectors may employ or be fabricated by the materials,structures, and techniques. More generally, organic devices, such asorganic transistors, may employ the materials, structures, andtechniques.

In some embodiments, an OLED fabricated using devices and techniquesdisclosed herein may have one or more characteristics selected from thegroup consisting of being flexible, being rollable, being foldable,being stretchable, and being curved, and may be transparent orsemi-transparent. In some embodiments, the OLED further comprises alayer comprising carbon nanotubes.

In some embodiments, an OLED fabricated using the devices and techniquesdisclosed herein further comprises a layer comprising a delayedfluorescent emitter. In some embodiments, the OLED comprises a RGB pixelarrangement or white plus color filter pixel arrangement. In someembodiments, the OLED is a mobile device, a hand held device, or awearable device. In some embodiments, the OLED is a display panel havingless than 10 inch diagonal or 50 square inch area. In some embodiments,the OLED is a display panel having at least 10 inch diagonal or 50square inch area. In some embodiments, the OLED is a lighting panel.

In some embodiments of the emissive region, the emissive region furthercomprises a host.

In some embodiments, the compound can be an emissive dopant. In someembodiments, the compound can produce emissions via phosphorescence,fluorescence, thermally activated delayed fluorescence, i.e., TADF (alsoreferred to as E-type delayed fluorescence), triplet-tripletannihilation, or combinations of these processes.

An OLED fabricated according to techniques and devices disclosed hereincan be incorporated into one or more of a consumer product, anelectronic component module, and a lighting panel. The organic layer canbe an emissive layer and the compound can be an emissive dopant in someembodiments, while the compound can be a non-emissive dopant in otherembodiments.

The organic layer can also include a host. In some embodiments, two ormore hosts are preferred. In some embodiments, the hosts used maybe a)bipolar, b) electron transporting, c) hole transporting or d) wide bandgap materials that play little role in charge transport. In someembodiments, the host can include a metal complex. The host can be aninorganic compound.

Combination with Other Materials

The materials described herein as useful for a particular layer in anorganic light emitting device may be used in combination with a widevariety of other materials present in the device. For example, emissivedopants disclosed herein may be used in conjunction with a wide varietyof hosts, transport layers, blocking layers, injection layers,electrodes and other layers that may be present. The materials describedor referred to below are non-limiting examples of materials that may beuseful in combination with the compounds disclosed herein, and one ofskill in the art can readily consult the literature to identify othermaterials that may be useful in combination.

Various materials may be used for the various emissive and non-emissivelayers and arrangements disclosed herein. Examples of suitable materialsare disclosed in U.S. Patent Application Publication No. 2017/0229663,which is incorporated by reference in its entirety.

Conductivity Dopants:

A charge transport layer can be doped with conductivity dopants tosubstantially alter its density of charge carriers, which will in turnalter its conductivity. The conductivity is increased by generatingcharge carriers in the matrix material, and depending on the type ofdopant, a change in the Fermi level of the semiconductor may also beachieved. Hole-transporting layer can be doped by p-type conductivitydopants and n-type conductivity dopants are used in theelectron-transporting layer.

HIL/HTL:

A hole injecting/transporting material to be used in the presentinvention is not particularly limited, and any compound may be used aslong as the compound is typically used as a hole injecting/transportingmaterial.

EBL:

An electron blocking layer (EBL) may be used to reduce the number ofelectrons and/or excitons that leave the emissive layer. The presence ofsuch a blocking layer in a device may result in substantially higherefficiencies, and or longer lifetime, as compared to a similar devicelacking a blocking layer. Also, a blocking layer may be used to confineemission to a desired region of an OLED. In some embodiments, the EBLmaterial has a higher LUMO (closer to the vacuum level) and/or highertriplet energy than the emitter closest to the EBL interface. In someembodiments, the EBL material has a higher LUMO (closer to the vacuumlevel) and or higher triplet energy than one or more of the hostsclosest to the EBL interface. In one aspect, the compound used in EBLcontains the same molecule or the same functional groups used as one ofthe hosts described below.

Host:

The light emitting layer of the organic EL device of the presentinvention preferably contains at least a metal complex as light emittingmaterial, and may contain a host material using the metal complex as adopant material. Examples of the host material are not particularlylimited, and any metal complexes or organic compounds may be used aslong as the triplet energy of the host is larger than that of thedopant. Any host material may be used with any dopant so long as thetriplet criteria is satisfied.

HBL:

A hole blocking layer (HBL) may be used to reduce the number of holesand/or excitons that leave the emissive layer. The presence of such ablocking layer in a device may result in substantially higherefficiencies and/or longer lifetime as compared to a similar devicelacking a blocking layer. Also, a blocking layer may be used to confineemission to a desired region of an OLED. In some embodiments, the HBLmaterial has a lower HOMO (further from the vacuum level) and or highertriplet energy than the emitter closest to the HBL interface. In someembodiments, the HBL material has a lower HOMO (further from the vacuumlevel) and or higher triplet energy than one or more of the hostsclosest to the HBL interface.

ETL:

An electron transport layer (ETL) may include a material capable oftransporting electrons. The electron transport layer may be intrinsic(undoped), or doped. Doping may be used to enhance conductivity.Examples of the ETL material are not particularly limited, and any metalcomplexes or organic compounds may be used as long as they are typicallyused to transport electrons.

Charge Generation Layer (CGL)

In tandem or stacked OLEDs, the CGL plays an essential role in theperformance, which is composed of an n-doped layer and a p-doped layerfor injection of electrons and holes, respectively. Electrons and holesare supplied from the CGL and electrodes. The consumed electrons andholes in the CGL are refilled by the electrons and holes injected fromthe cathode and anode, respectively; then, the bipolar currents reach asteady state gradually. Typical CGL materials include n and pconductivity dopants used in the transport layers.

As previously described, various systems, devices and techniques may beused to fabricate OLEDs and devices containing OLEDs. One such techniqueis OVJP, in which material such as organic emissive material is directedin a jet ejected from a nozzle toward a substrate. Recent OVJP systemsincorporate a delivery-exhaust-confinement (DEC) arrangement. Forexample, DEC-type arrangements disclosed in U.S. Patent Publication No.2015/0376787, the disclosure of which is incorporated by reference inits entirety, use convection to confine deposition of the organic vaporinto a desired printing zone. As another example, U.S. PatentPublication No. 2017/0294615, the disclosure of which is incorporated byreference in its entirety, describes DEC depositor having modifieddelivery apertures that may improve the thickness uniformity of printedthin film features over a central region of interest. For example, thedelivery aperture of the depositor may be split into two offsetsections.

Embodiments disclosed herein provide OVJP depositors that print thinfilm features that are highly uniform in thickness over the active areaof printed devices. The OVJP depositors disclosed herein may differ fromconventional OVJP nozzles in that, for example, the delivery aperturesidewall is arranged to act as a semi-diverging nozzle. Furthermore,devices disclosed herein may incorporate trapezoidal delivery aperturesand/or pairs of mirror-image depositors that are arranged in offsetranks along the print direction. Depositors as disclosed herein mayprovide improved deposition rates and/or process stability relative toconventional OVJP deposition systems.

It has been found that the uniformity and deposition efficiency achievedin OVJP may be improved by flaring the inner sidewall of the deliveryaperture of a split-depositor aperture to form a diverging deliveryaperture. FIGS. 3A-3B show such a depositor according to an embodiment.FIG. 3A shows a surface of the depositor as viewed from the substrate.FIG. 3B shows a cross section of the depositor taken across the dashedline 301 through the facial section shown in FIG. 3A. The deliveryapertures 302 are split and offset from each other along the centerline303 of the depositor to increase the uniformity of organic thin filmdeposition over the printing target. A split depositor arrangement asshown in FIG. 3 is described in further detail in U.S. Patent Pub. No.2017/0294615, the disclosure of which is incorporated by reference inits entirety. As shown in FIG. 3A, in some embodiments the deliveryapertures 302 may be arranged between the exhaust apertures 309, suchthat a line drawn between and perpendicular to the two exhaust aperturescrosses only one of the delivery apertures. This and other arrangementsdisclosed in U.S. Patent Pub. No. 2017/0294615 may be used with any ofthe various depositor arrangements and modifications disclosed herein.

The delivery aperture is in fluid communication with a delivery channel304 that transports organic vapor entrained in an inert carrier gas froma sublimation source to a substrate 305 beneath the print head. Thedelivery channel is bounded in its cross section by two sides, a widespacer 306 and a narrow spacer 307. The spacers separate the deliverychannels from the exhaust channels 308. The exhaust channels terminatein exhaust apertures 309, and may connect the exhaust apertures 309 to avacuum source. The junction between the delivery aperture and thedelivery channel contains a diverging section 310, such that thesidewall flares outward relative to the delivery channel on the side ofthe wide spacer and the wide spacer tapers to become narrower at itstip. That is, the delivery channel 304 includes a diverging portion 310that is wider than the portion that is farther from the deliveryaperture 302 than the diverging portion 310. The different portions forma single delivery channel such that they are all in direct fluidcommunication in a channel leading through the depositor to the deliveryaperture. The width and, more generally, the shape of the deliveryaperture 302 may be the same as the width and shape of the divergingportion of the delivery channel 310, i.e., the delivery channel 310 maydiverge at an end portion closest to the delivery aperture, ending inthe delivery aperture itself. Crosswise channels formed by recesses inthe depositor surfaces 311 may provide high conduction paths forconfinement gas to ensure its even distribution along the length of thedepositor.

FIG. 4 shows an expanded view of a depositor as shown in FIG. 3 toillustrate various portions and dimensions of the arrangement. The widthof the delivery channel upstream of the divergence is D 401. The widthof the exhaust channel is E 402. The widths of the narrow and widespacers are DE1 403 and DE2 404, respectively. The fly height separationbetween the depositor and the substrate is g 405.

The divergence of the delivery aperture may be characterized by theflare width FW 406 and the angle θ 407 of the upper bound of the anglewith respect to the surface of the depositor facing the substrate, asshown. The flare angle θ (407) may be in the range 30-60° or, moregenerally, any angle that provides the desired width and flare width forthe delivery channel and aperture, as disclosed in further detailherein. In general, smaller printed features may benefit from a higherflare angle, while for larger printed features a relatively smallerangle may be preferred. A three-dimensional rendering of the depositoris shown in FIG. 5. The flared wall 501 of the delivery channel isvisible through the delivery apertures 302. In some embodiments,multiple depositors may be arranged in a microfabricated linear array502 contained within a print head.

Examples cross-sectional deposition profiles generated on a substrate bydepositors with varying degrees of divergence are shown in FIG. 6. Theoffset from the centerline of the deposited feature is indicated inmicrons by the horizontal axis 601 and the normalized thin filmthickness is indicated by the vertical axis 602. Flare widths of FW=0(603), 4 μm (604), 8 μm (605), and 12 μm (606) are shown. The featureprofile generated by the FW=0 case, i.e., no flare, shows two pronouncedpeaks around a pronounced central depression. This may adversely affectthe thickness uniformity of the feature. The depression becomesprogressively smaller for the FW=4 μm and 8 μm cases, improvinguniformity. The central depression is due to the offset between the twosections of the delivery aperture creating a region of low organic fluxtowards the centerline of the depositor. The divergence at the end ofthe delivery channel redirects more delivery gas and organic vapor fluxtowards the centerline, thereby evening the deposition profile as shown.

If the divergence is more pronounced, the center of feature may becomeconvex, as it does for a flare width FW of 12 μm, and thicknessuniformity will decrease. It has thus been found that, in thisarrangement, the optimum degree of divergence to achieve a printedfeature with acceptable thickness uniformity around the central portionof the deposited feature is between 8 and 12 μm. As described herein,the “uniformity” of a deposited feature is defined as one minus thedifference between the maximum and minimum thicknesses within aspecified width about the middle of the feature, normalized to theaverage thickness over this width. The uniformity over 50 μm (“U50”),generally is used as a performance metric for depositors. The U50 valuesfor flare widths as previously disclosed are provided in Table 1:

TABLE 1 FW (μm) U₅₀ 0 0.829 4 0.926 8 0.933 12 0.907

These U50 results would suggest that a flare width of 8 μm is optimal.More generally, in some embodiments flare widths in the range of 6-10μm, 6-12 μm, 8-10 μm, or 8-12 μm may be preferred. However, theuniformity and deposition rates should be considered together todetermine the full utility of diverging delivery apertures. FIGS. 7A and7B show contour plots of the U50 attainable by different depositordesigns at fly heights of g=30 μm and g=45 μm, respectively. Thehorizontal axis 703 indicates DE2 and the vertical axis 704 indicatesFW, both measured in microns. As is evident from these examples, thewidth DE2 largely controls the uniformity of printed features. In somecases there may be an optimal value of DE2 to achieve the highest degreeof uniformity as previously defined for a given fly height. However, thepotentially optimal value is not always sufficient to achieve a desireduniformity level, particularly at lower fly heights. Adding divergenceto the delivery aperture provides another method for improvinguniformity. For example, if a U50 of 95% or more is desired at a givenfly height, then it may be desirable for the depositor to occupy aregion of the design space 705 enclosed by the 0.95 contour. Thisoccupies the upper right portion of the graph in both cases, and soindicates a diverging delivery aperture with FW greater than 0.Operating the depositor at a lower fly height generally reduces thewindow of acceptable designs while increasing the amount of divergencerequired.

The deposition rate of the depositor depends both on the quantity ofvapor ejected by the delivery aperture and on the efficiency η of thedepositor, defined as the fraction of vapor ejected from the deliveryaperture that adsorbs to the substrate. The deposited feature size isdescribed by the full width to 5% of maximum thickness (FW5M) of theprinted profile. FIGS. 8A and 8B show plots of feature size 801 anddepositor efficiency 802 as a function of fly height, for a depositorwith DE2=60 μm. The fly height is given in microns on the horizontalaxis 803, while the resulting FW5M in microns and η are shown on thevertical axes, respectively. Curves are plotted for cases of FW=0 μm 806(solid), 4 μm 807 (broken), 8 μm 808 (dash), 12 μm 809 (dot), and 15 μm810 (dot dash).

As shown by FIGS. 8A-8B, it has been found that the depositor efficiencytrends downward with increasing fly height. Accordingly, operating at alower fly height generally is advantageous because it increasesdeposition rate, provided the fly height separation can be accuratelymaintained. In contrast, the feature size remains relatively constantwith fly height and does not follow a clear trend.

The addition of divergence to the delivery aperture as disclosed hereinhas been found to reduce the feature size as measured by FW5M in allcases, with greater reduction resulting from a greater degree ofdivergence. Furthermore, the use of a diverging delivery channel doesnot significantly affect the deposition rate for a constant value of DE2width and fly height, so the diverging channel may be used withoutpenalty. Additionally, considering only the quantity of materialdeposited within the uniformity control width of 50 μm about the featurecenter, the diverging delivery aperture improves utilization efficiency.As shown in FIG. 6, the centers of the printed profiles are not onlyflatter, but they have a greater average thickness. The divergingaperture also has no detrimental effect on feature resolution, and infact, improves it. Thus the diverging aperture allows for features withhigh thickness uniformity to be printed at low fly height, improvingdepositor efficiency and therefore deposition rate.

Depositor performance can be understood by the figure of merit FOM asdefined in Equation 1. The FOM approaches zero past cutoffs for featuresize and uniformity beyond which the depositor ceases to be useful forits intended application. Additional value is given for being wellinside feature size and uniformity specifications, but this becomesasymptotically less as the specification is exceeded. In this case, theFW5M specification is 145 μm and the U50 specification is 95% in thepresented application. The FOM depends linearly on η. A more efficientdepositor is better, but there is no hard cutoff. The higher the FOM,the better the depositor is expected to perform.

$\begin{matrix}{{FOM} = {{\eta \left( {1 + {\tanh \left( \frac{U_{50} - {95\%}}{2.5\%} \right)}} \right)}\left( {1 - {\tanh \left( \frac{{{FW}\; 5M} - {145\mspace{14mu} {µm}}}{2.5{um}} \right)}} \right)}} & (1)\end{matrix}$

A matrix of simulated depositors with DE2 from 40 to 90 μm, and FW from4 to 15 μm were studied at fly heights ranging from 25 to 90 μm. Themaximum FOM at each fly height is plotted in FIG. 9 as a function of flyheight. The FOM is indicated on the vertical axis 901. The maximum FOMattainable at each fly height decreases, primarily because of thedecrease in deposition efficiency. A maximum FOM of 0.78 is obtained atg=30 μm. Thus, in this example, the depositor should be operatedrelatively close to the substrate (30 μm) for best performance. Thediverging delivery aperture allows the depositor to print features withgood uniformity while operated in this position, as previouslyindicated.

The deposition profile generated by the top half of the depositor isshown in FIG. 10 for divergences of FW=0 (1001), 4 μm (1002), 8 μm(1003), 12 μm (1004) and 15 μm (1005). The leftmost portion of thedistribution is generated by vapor flowing from the delivery aperture tothe far exhaust aperture, while the right side is generated by vaporflowing from the delivery aperture to the near exhaust aperture. Theslope on the left slide of the distribution becomes more linear as thedivergence FW increases, since the diverging sidewall of the aperturedirects more flow inward across the centerline. At the same time, theleft side of the deposition profile moves inward slightly withincreasing divergence, leading to a reduction in the FW5M when thefeatures are overlaid.

The net deposition profile is a superposition of material from the twodepositor halves, i.e., the profile shown in FIG. 10 and a mirror imageof it. The sum of the two profiles is flatter if the slopes of theoverlapping portions are linear. The addition of two deposition profilesis illustrated as the overlap of a solid line profile and a dashed lineprofile in FIGS. 11A-11B. As shown in FIG. 11A, two mirror-imageprofiles with linear sidewalls 1101 produce a mesa-like feature 1102when superposed with one another. The separation of the two profilesaffects the width of the flat region, but it does not affect theuniformity within that width. This makes feature uniformity lesssusceptible to perturbation.

For comparison, FIG. 11B shows two profiles of a Gaussian shape 1103.When added, the combined profile is not only less uniform than theexample shown in FIG. 11A, but its uniformity is more sensitive toprocess conditions. For example, the profiles may add to a combinedprofile with a single broader peak 1104, or they may add to a doublepeaked profile 1105.

Cases where diverging apertures were formed by tapering the narrowspacer between the delivery and exhaust channels were also evaluated.Creating a diverging nozzle in this way did not improve printingresolution or uniformity, but it did adversely affect depositorefficiency. It has been found that diverging apertures formed bytapering the wide DE spacer are useful.

In an embodiment, the uniformity and deposition efficiency achieved byan OVJP print head can be further enhanced by shaping the deliveryaperture such that the maximum organic vapor flux onto the substrate isshifted towards the ends of the depositors. In an embodiment, this maybe achieved by tapering the delivery aperture of the depositor such thatit is wider at its ends than at the center of the depositor. FIG. 12Ashows an example of such a depositor arrangement as viewed from thesubstrate, i.e., below the depositor during conventional operation. Thedelivery apertures 1201 are isosceles trapezoids with their shortparallel edges 1202 at the depositor centerline 1203 and long paralleledges at the ends of the depositor. Trapezoidal aperture sectionsmeeting at the centerline form a bowtie shape, as is apparent for theexhaust apertures 1205. As before, the delivery apertures are split andoffset from each other along the centerline of the depositor to increasethe uniformity of organic thin film deposition 1206. The degree ofoffset is defined as Δ=DE2−DE1. The width of the short parallel side isthe nominal aperture width. The degree of taper can be expressed as theangle α 1207 between a center long axis of the delivery aperture and onelong edge of the depositor aperture. In some embodiments, the exhaustapertures 1205 and/or the delivery apertures 1201 may be trapezoidal asshown. Alternatively, one or more apertures may be rectangular while theother apertures are trapezoidal.

If the depositor is made by the techniques described in US Pub. No.2015/0376787, the taper may be formed from an undercut generated by deepreactive ion etching (DRIE). The undercut can be tuned to optimize thedelivery aperture, but it also affects the exhaust apertures and theface of the depositor. This can be seen in a three-dimensional renderingof the depositor as shown in FIG. 12B. The centerline of the depositoris raised relative to its ends. The shape of the surfaces to the frontand rear 1208 of the depositor are not believed to be critical to thisapplication. Recesses to the right and left of the depositor 1209 formcrosswise channels to promote the even flow of confinement gas into thedeposition zone. The walls of these channels may also be subject toundercut, but this is not critical.

The dominant effect of undercut is to force gas flowing through thedelivery aperture towards the ends of the depositor. This leads to morerapid deposition of organic material towards the ends of the depositor.FIG. 13 shows a photograph of a thin film deposited by a stationarydepositor as previously described, which illustrates this effect. Thesplit channels generate two regions of relatively intense deposition,one in the upper left quadrant 1301 and the other in the lower rightquadrant 1302. Considering a point on either of these regions that isrelatively close to the depositor centerline 1303, there areapproximately 1.5 thin film interference fringes between it and theboundary of the deposition zone 1304. This indicates a film thickness ofapproximately 220 nm. Points further from the centerline 1305 show twofull interference fringes, indicating a film thickness of 290 nm. Thus,it can be seen that the deposition is biased towards the outside of thedepositor.

The local width of a channel may have a disproportionate effect on thelocal flow through a given section of a long aperture. Assuming that gasflowing through the narrowest portion of the channel behaves as alubrication flow, then the flow per length q scales as the third powerof the local channel width. The flow through an isosceles trapezoidchannel given as an example in FIG. 3 is given by Equation 2:

$\begin{matrix}{q = {\frac{4Q}{{l\left( {w_{1} + w_{2}} \right)}\left( {w_{1}^{2} + w_{2}^{2}} \right)}\left( {w_{1} + {\frac{w_{2} - w_{1}}{l}z}} \right)^{3}}} & (2)\end{matrix}$

The nominal width at the center is w₁ and the width at the end is w₂. Anormalized graph of q through a delivery channel that is 400 μm long, 15μm wide at its center, and with an angle α of 1.7° is shown in FIG. 14.The flow per unit length through the delivery aperture is shown on thevertical axis 1401 as a function of position with respect to thedepositor centerline on the horizontal axis 1402. The flow through thedelivery aperture is shown as a solid line 1403, normalized such that aflow of 1 passes through the midline of the depositor. Flow through theouter portions of the delivery aperture is nearly six times the flowthrough the center. The flow through an exhaust aperture with acenterline width of 25 μm is shown as a dotted line at 1404, alsonormalized to have a value of 1 at the depositor midline. The change inexhaust flow is proportionally less than that of the delivery flow alongthe length of the depositor. The exhaust channel has a greatercenterline width, so the undercut leads to less relative change in widthalong its length. The ratio of delivery flow to exhaust flow is,therefore, greater at the ends of the depositor than at the center andmore organic material reaches the substrate at the ends of thedepositor. Undercuts of the exhaust channel and the depositor face bothtend to force deposition inward, but their effects are small relative tothe undercut of the delivery channel.

FIG. 15A shows deposition profiles generated by depositors with varyingdegrees of undercut. Deposition profiles are shown for undercuts ofα=1.7° (1501), 1.1° (1502), 0.57° (1503) and 0 (1504). The depositionprofiles generated by depositors for which the aperture tapers andbecomes narrower further from the centerline are plotted for α of −0.57°(1505) −1.1° (1506) and −1.7° (1507). As shown, it was found that bothdeposition rate and uniformity increase with greater α and, conversely,decrease with negative a. The deposition rate scales with the area undereach curve, so taller curves represent faster deposition and moreefficient utilization of material. Uniformity is determined by theflatness of the deposition profile near its center as previouslydescribed. Apertures with α less than 0 produce deposition profiles withtwo peaks (1508), corresponding to the position of the deliveryapertures and a valley between them. This peaked structure reducesuniformity, and the flatter profiles generated by apertures withpositive α values are preferable. The marginal benefit of increasing αfrom 1.1° and 1.7° is minimal, suggesting that α values in this rangeare optimal or near optimal. That is, in embodiments disclosed herein itmay be preferred to use trapezoidal delivery apertures having α in therange of 1.1-1.7° or, more generally, 1.0-2.0°. In some embodiments, itmay be preferred to have α of about 1.7° or, more generally, 1.5-1.9°,1.6-1.8°, or the like.

The cases of rectangular apertures with α=0 and trapezoidal apertureswith α=1.7° are compared in FIG. 15B. The thickness uniformity, U50, isdefined as the maximum thickness less the minimum thickness over theaverage thickness over a width of 50 μm across the center of thefeature, shown at 1509 for reference. The difference between the maximumand minimum over this range is much less for the trapezoidal apertures1510 than for the rectangular apertures 1511. The U50 for thetrapezoidal depositors is 96%, compared with 86% for rectangulardepositors. Likewise, the efficiency η with which material is depositedon the substrate increases from 15.8% to 16.8% for the trapezoidaldepositor apertures compared to rectangular. The feature size, definedas the full width of the deposition profile to 5% of its maximum (FW5M),increases by only 1.2 μm, going from 133.6 μm for the rectangularaperture to 134.8 μm for the trapezoidal aperture.

The utility of trapezoidal apertures can further be shown by aparametric study in fly height g for four different channel geometrieswith split delivery apertures. The channel geometries are defined by αand the center-to-center separation of the delivery aperture Δ and asindicated in Table 2:

TABLE 2 Depositor Δ (μm) α (deg) A 45 0 B 45 1.7 C 55 0 D 55 1.7

Feature uniformity is normally very sensitive to fly height. Atrapezoidal aperture configuration can reduce the sensitivity of U50 aspreviously defined to fly height for a given feature size and fly heightrange. FIG. 16 shows plots of U50 for depositors A-D shown in Table 2(1601 to 1604, respectively) as a function of fly height. The verticalaxis 1605 indicates U50. All of the curves have approximately the samemaximum of U50=0.96, but the curves 1602, 1604 for depositors withα=1.7° have a broader maximum than the curves 1601, 1603 for depositorsA and C with α=0. This indicates that U50 is less sensitive to flyheight variation within the region of interest for printing fortrapezoidal apertures compared with rectangular apertures. Furthermore,curves B and D have their uniformity maxima at a lower fly height than Aand C respectively.

The deposition rate for each of the four depositors described in Table 2is plotted in FIG. 17A as a function of fly height. The deposition rateindicated on the vertical axis 1701 is normalized. The deposition ratecurves are plotted for depositors A-D as 1702, 1703, 1704, and 1705,respectively. It was found that depositors with larger Δ deposit at ahigher rate, while depositors with greater α have a higher depositionrate for a given Δ. The associated feature size is plotted in FIG. 17Bas a function of fly height. Curves are shown for depositors A-D as1706-1709, respectively. It can be seen that the feature size isprimarily determined by Δ and is relatively insensitive to α for flyheights less than 50 μm. For g greater than 50 μm, the feature sizeincreases more rapidly for nonzero α.

These data also indicate that depositors with greater Δ or α yieldgreater deposition rates. Furthermore, the presence of a taper such thatα is greater than zero reduces the optimal fly height for a given Δ. Asbefore, lower fly heights generally are preferable due to greaterdeposition efficiency. Since feature size does not increase with α atlow fly height, a trapezoidal depositor allows deposition rate anduniformity can be improved without penalty by operating at a lower flyheight.

FIG. 18 shows the FOM as previously defined as functions of fly height.The FOM is indicated on the vertical axis 1801 and curves are plottedfor depositors A, B, C, and D 1801-1805, respectively. Each depositorhas an optimal fly height at which its figure of merit is optimized. Aswith the deposition uniformity, the optimal fly height tends to increasewith Δ and α. Depositor D, which has a trapezoidal design, has thegreatest value of its FOM maximum. Furthermore, the curve for depositorD has a broader peak than the next highest curve, which is depositor A.This implies that the performance of depositor D is less dependent onfly height than that of A. The trapezoidal design permits uniformity andfeature size specifications to be met while allowing greater depositionrate and stability with fly height.

The field of organic flux onto the substrate generated by depositors Cand D are plotted in FIGS. 19A and 19B, respectively. The horizontalaxis 1901 gives distance orthogonal to the direction of printing,measured from the middle of the depositor, in microns. The vertical 1902axis gives distance parallel to the direction of printing, measured fromthe depositor midline in microns. Contours 1903 give the strength oforganic flux onto the substrate in arbitrary units. It can be seen thanFIG. 19B is a better match for the experimental result pictured in FIG.13 than FIG. 19A, indicating that undercut apertures affect simulatedand experimental results similarly One relevant difference between theflux fields in FIGS. 19A and 19B is that the plume of intense depositionextends further across the spacer between the delivery channel and thefar exhaust in the case of the trapezoidal apertures 1904 compared withthe rectangular apertures 1905.

As with the flared depositor, this extra flux makes the thicknessprofile of material deposited by each half depositor more linear withinthe zone where they add. The deposition profile generated by the tophalf of the depositor is shown in FIG. 20 for undercuts of α=1.7°(2001), 1.1° (2002), 0.57° (2003) and 0° (2004). The leftmost portion ofthe distribution (to the left of the peak) is generated by vapor flowingfrom the delivery aperture to the near exhaust aperture, while the rightportion is generated by vapor flowing from the delivery aperture to thefar exhaust aperture. The slope on the right slide of the distributionbecomes more linear as a increases.

The use of flared and/or trapezoidal delivery apertures may be subjectto the constraint that Δ=DE2−DE1. Therefore, the shape of the thicknessprofile set down by each half of the depositor is dependent on theoffset between the two halves of the depositor. In some embodiments, therelationship between DE1, DE2 and Δ can be broken by separating thedepositor into two separate ranks. FIG. 21 shows an example arrangementof depositor apertures that include two ranks. In this arrangement, boththe delivery aperture 2101 and exhaust aperture 2102 are discontinuous.The upper rank 2103 and lower rank 2104 are mirror images of each other,as the depositor halves were before, but the centers of the deliveryapertures are now offset from each other by a distance ϕ 2105. Here thecenter is defined as the midline between the outer edges of the exhaustaperture on each depositor half, shown at 2106. In this configuration,Δ=DE2−DE1+ϕ. The arrangement of separate ranks may be described in termsof their position relative to one another during use of the depositor todeposit material on a substrate. Generally, the depositor and thesubstrate will be in relative motion during material deposition. Forexample, the depositor may move relative to the substrate in a direction2150 as shown. The apertures in such a configuration may be described asbeing in a “leading” or “trailing” position in that case. For example,the upper rank 2103 may be described as being in a “leading” positionrelative to the lower rank 2104, since it is disposed in a more forwardposition on the depositor when the depositor is operated. Similarly, anaxis of the depositor and/or any set of apertures in the depositor thatis parallel to the direction of relative movement 2150 may be referredto as a “leading/trailing axis” of the depositor or of the apertures. Insome embodiments, one or more ranks of delivery and/or exhaust aperturesmay be disposed on a depositor relative to the leading/trailing axis soas to deposit material along a consistent desired path relative to themovement.

In an embodiment, the depositors may be arranged in one or more lineararrays as shown in the example three-dimensional view of FIG. 22. Eachline of depositor halves may be referred to as a rank. The first rank2201 is located along the lower portion of the die edge and the secondrank is on the upper portion 2202. A printed feature is complete whenboth ranks of the depositor make a printing pass over it. Transverseconfinement gas channels 2203 remain aligned and normal to the die face2204 through both ranks of the depositor.

Various geometries may be used for the separate depositor halves.Several examples are listed in Table 3:

TABLE 3 Depositor DE1 (μm) DE2 (μm) A 10 10 B 10 30 C 10 40 D 20 30 E 2040

FIG. 23 shows example deposition profiles for depositors having thegeometries shown in Table 3. Profiles for depositors A-E are shown asprofiles 2301-2305, respectively. A sharp transition between printed andnon-printed zones generally requires a narrow DE1 spacer, since DE1defines the outer edge of the printed pattern. At the same time, a widerDE2 spacer makes thickness slope of the inner edge of each half patternmore gentle and linear. Adjusting DE2 and ϕ controls the width of thelinear region of the printed feature.

FIG. 24 shows the added profiles for two depositor halves for adepositor having configuration B in Table 3. Profile traces for ϕ=−5 μm,0 μ, 10 μm, 25 μm, and 35 μm are plotted as 2401, 2402, 2404, 2405, and2406, respectively. It can be seen that the resulting traces are moresharply peaked for lower values of ϕ and flatter for larger ϕ. The ϕ=0case reflects the same profile resulting from the case of a depositorwith a split delivery aperture as previously disclosed. The peaksgenerated by the two halves of the depositor are insufficientlyseparated, so a peaked thickness profile is produced. The width overwhich the thickness of the printed feature is uniform significantlyincreases in the ϕ=25 μm case. Due to the additional offset between thetwo ranks of the depositor, the U50 value for this arrangement is 97.4%.

Depositors with small DE spacers, such as depositors A and B, may besuitable for deposition of subpixels for RGB arrays with a very finepixel pitch, like 8K displays. The pixel geometry of such a device mayrequire a mix of wider and narrower subpixels due to differences insurface area of each color of device. An example of such a pixelarrangement is shown in FIG. 25. The overall pixel 2501 is a square 190μm on a side. The blue subpixel 2502 is 50 μm wide, while the green andred subpixels 2503, 2504, respectively, are 25 μm wide. The active areasof each subpixel are surrounded by a 30 μm wide inactive border 2505between them. The thickness profile of a printed feature may extend intothe border, but not into a neighboring active region. The blue featuremay be no wider than 110 μm, while the red and green features must beless than 85 μm wide.

FIG. 26A shows a profile generated by a depositor having configuration Bat ϕ=25 μm for a blue subpixel, such as for use in a full-color OLEDdevice. The width of the active area of the blue subpixel 2601 and thewidth of the borders 2602 are shown. The uniformity in the active areais excellent. The feature width FW5M is 94.3 μm and the entire width ofdeposition is enclosed within the borders. In contrast, a profilegenerated by a depositor having configuration A at ϕ=27.5 μm, forexample for a red or green subpixel, is shown in FIG. 26B. The width ofthe active area of the subpixel 2603 and the border widths 2602 areshown. In this case, the U25 uniformity (i.e., uniformity over 25 μm),is a more meaningful uniformity measurement than U50 for the depositor,since the active area is narrower. The U25 uniformity of this printedfeature is 96.0% and the FW5M feature size is 74.6 μm.

The transition width between printed and non-printed zones must benarrower than the borders in all cases, so sidewall profilespecification for all printed features is similar. This defines DE1. Thedepositor printing the blue subpixel, however, must maintain uniformityover a wider region than the depositors depositing red and greensubpixels. Likewise, the feature size of the depositor printing the redand green subpixels must be smaller than is permitted of the bluedepositor. The ability to adjust Δ independently of DE1 and DE2 makes itpossible to design depositors for both subpixel dimensions. The two rankdesign can be combined with either flared delivery channels ortrapezoidal delivery apertures to provide further degrees of designfreedom to improve feature uniformity. Furthermore, dice with three ormore ranks of depositors may be used.

A two-rank depositor as disclosed herein may be fabricated using atechnique such as those disclosed in US Patent Pub. No. 2015/0376787,with the addition of an additional wafer. Each die may be formed fromthe bonding of three Si layers with etched trenches. FIG. 27A shows anexample arrangement of depositor faces split between wafers layers. Inthis arrangement, the inner surface of the bottom wafer of the stack2701 may be etched with trenches 2702 that become the apertures of thefirst depositor rank. The trenches 2702 may have corresponding trenches2703 on the lower surface of the middle wafer 2704, which formlengthened apertures when the wafers are bonded. Trenches 2705 for thesecond rank may be etched into the inner surface of the top wafer 2706of the stack. These trenches 2705 may have corresponding trenches on thetop surface 2707 of the middle wafer. Recesses 2708 that form crosswisechannels for confinement gas flow may be aligned between the waferlayers.

FIG. 27B shows an example arrangement for routing for the delivery andexhaust channels according to an embodiment of a depositor as disclosedherein. The die is shown in cross section normal to the connecting eachrank of depositor halves. The delivery flow may be routed through commondelivery channels 2709 that are formed from trenches between the bottomand middle wafers as previously disclosed with respect to FIG. 27A. Thedelivery flow may be fed into the array through a delivery via 2710arranged normal to the die face. The exhaust flow may be routed throughcommon exhaust channels 2711 formed from trenches between the middle andtop wafers as previously disclosed. The exhaust flow may exit thedepositor through an exhaust via 2712 that is also normal to the dieface. The common delivery and exhaust channels may be positioned onseparate levels of the wafer stack, but each may serve both ranks ofdepositor halves 2713. A crossover zone 2714 adjacent to the depositorhalves may contain internal vias that permit local delivery and exhaustchannels of each rank to connect with the common delivery and exhaustchannels.

FIG. 28A shows an example channel arrangement for a first depositor rankaccording to an embodiment disclosed herein. In this arrangement, thedelivery aperture 2801 connects to a local delivery via 2802 through alocal delivery channel 2803. The local delivery via connects to adelivery plenum in the second rank. The exhaust apertures 2804 connectto local exhaust channels 2805 which combine with local exhaust channelsfrom adjacent exhaust apertures in the same rank into an exhaust plenum2806. The plenum also captures exhaust flow from the second depositorrank exhaust apertures through a local exhaust via 2807. Exhaust plenumsmay be connected to common exhaust channels 2808. Common exhaustchannels may widen or merge further downstream.

FIG. 28A shows an example channel arrangement for a second depositorrank according to an embodiment disclosed herein, which may be used inconjunction with the first rank arrangement shown in FIG. 28A. In thisarrangement, the delivery aperture is connected to a delivery plenum2809 that also distributes delivery flow to the first depositor rankthrough a local delivery via. A common delivery channel 2810 ispositioned upstream of the delivery plenum. Exhaust apertures fromadjacent depositors are connected to local exhaust vias by local exhaustchannels. A local exhaust via connects to the exhaust plenum in thefirst depositor rank.

EXPERIMENTAL

Depositors were modeled using COMSOL Multiphysics 5.3 using laminarflow, heat transfer, and species mixing modules. The chamber ambientsurrounding the depositor was assumed to be argon at an absolutepressure of 200 Torr, while the gas introduced through the deliveryaperture was helium. The depositor temperature was 350 C. Organic vaporwas treated as a dilute gas entrained in the delivery flow.

The dimensions of the depositors with flared delivery apertures were:D=15 μm; E=25 μm; DE1=20 μm; θ=45°; DE2=60 μm; and g=30 μm unlessotherwise specified, with each dimension corresponding to thedefinitions previously described herein. The flow through the deliveryaperture (QD) was 6 sccm and the flow through the exhaust aperture (QE)was 24 sccm.

The dimensions of the trapezoidal delivery apertures were: D=15 μm; E=25μm; DE1=20 μm; and DE2=65 μm or 75 μm. All aperture and spacerdimensions are measured along the centerline depositor as previouslydisclosed. The flow rates QD and QE were 4.5 sccm and 18 sccm,respectively. The length of each half of the delivery aperture was 190μm and the length of each exhaust aperture was 450 μm for both theflared and trapezoidal depositors.

The delivery apertures of the two-rank depositors were 13×400 μm and theexhaust apertures were 15×450 μm. The fly height g was 30 μm. The QD andQE flows through each two-rank depositor were 12 sccm and 48 sccm,respectively.

A micronozzle array for trapezoidal architectures was fabricated by themethod described in US Patent Pub. No. 2015/0376787. As previouslydisclosed herein, a DRIE process as described in the '787 patentpublication may be tailored to generate a degree of undercut as itetches the channels downward. The undercut in the tested examplecorresponds to α=0.6°. The dimensions of the tested depositor were D=15μm; E=25 μm; DE1=20 μm; DE2=75 μm. The depositor was operated in a 200Torr argon ambient with a delivery flow of 6 sccm helium and an exhaustflow of 26 sccm. The depositor was heated to 350 C. The fly heightseparation between the substrate and depositor was 45 μm.

It is understood that the various embodiments described herein are byway of example only, and are not intended to limit the scope of theinvention. For example, many of the materials and structures describedherein may be substituted with other materials and structures withoutdeviating from the spirit of the invention. The present invention asclaimed may therefore include variations from the particular examplesand preferred embodiments described herein, as will be apparent to oneof skill in the art. It is understood that various theories as to whythe invention works are not intended to be limiting.

We claim:
 1. A device for deposition of a material onto a substrate, thedevice comprising: a nozzle block comprising: a first exhaust aperture;a second exhaust aperture; a first delivery channel having a first endthat forms a first delivery aperture disposed between the first exhaustaperture and the second exhaust aperture and closer to the first exhaustaperture than the second exhaust aperture; wherein the first deliverychannel is wider at a first portion than at a second portion, the firstportion being closer to the delivery aperture that the second portion,and wherein the first portion is in direct fluid communication with thefirst delivery aperture and the second portion is in direct fluidcommunication with the first portion.
 2. The device of claim 1, thenozzle block further comprising: a second delivery channel in the nozzleblock having a first end that forms a second delivery aperture disposedbetween the first exhaust aperture and the second exhaust aperture;wherein the second delivery aperture is offset from the first deliveryaperture along an axis of the nozzle.
 3. The device of claim 2, whereina side wall of the first portion of the delivery channel forms an angleof 30-60° with the surface of the nozzle block.
 4. The device of claim2, wherein the first exhaust aperture and the second exhaust apertureare rectangular, and the longest edge of each of the first exhaustaperture and the second exhaust aperture is arranged along a directionof relative movement of the device and the substrate when the device isin operation.
 5. The device of claim 1, wherein the delivery aperturehas a flare width of 6-12 μm.
 6. The device of claim 1, wherein, for anyline drawn between and perpendicular to the first exhaust aperture andthe second exhaust aperture, the line crosses no more than one of thefirst delivery aperture or the second delivery aperture.
 7. The deviceof claim 1, further comprising an external vacuum source in fluidcommunication with the first exhaust aperture and the second exhaustaperture.
 8. The device of claim 1, wherein the delivery aperture istrapezoidal.
 9. The device of claim 8, wherein the delivery aperture hasan angle α between a long center axis of the delivery aperture and alongest edge of the delivery aperture in the range of 1.1°-1.7°.
 10. Thedevice of claim 1, said nozzle block further comprising: a third exhaustaperture; a fourth exhaust aperture; a second delivery channel having afirst end that forms a second delivery aperture disposed between thethird exhaust aperture and the fourth exhaust aperture and closer to thefourth exhaust aperture than the third exhaust aperture; wherein thesecond delivery channel is wider at a first portion than at a secondportion, the first portion being closer to the second delivery aperturethat the second portion, and wherein the first portion is in directfluid communication with the first delivery aperture and the secondportion is in direct fluid communication with the first portion
 11. Thedevice of claim 10, wherein the second delivery channel, third exhaustaperture, and fourth exhaust aperture are disposed in a trailingposition in the nozzle block relative to the first delivery channel,first exhaust aperture, and second exhaust aperture.
 12. The device ofclaim 10, wherein the group of the first and second exhaust aperturesare offset from the group of the third and fourth delivery aperturesalong a direction perpendicular to a leading/trailing axis of thedevice.